1. Field of the Invention
The present invention relates to powder for a corrosion resistant sintered body having excellent ductility, specifically, relates to powder capable of maintaining a high elongation even after corrosion.
2. Description of the Related Art
Conventionally, a sensor ring which issues pulses having frequencies in proportion to rotation number of wheels in an anti-lock system of vehicle breaking system, has been used. The sensor ring is shaped as a whole in a ring having many gear like concave and convex in all outer circumference for causing the sensor ring to issue pulse signals of frequency in proportion to said wheel rotation number via an electromagnetic pick-up disposed in the vicinity of said gear like concave and convex.
The sensor ring has a complicated configuration in the whole. If it is composed in an ingot, processing costs are made expensive. As a result, conventionally, the sensor ring is composed of a powder sintered body.
As materials for this kind of sensor ring, powders of ferrite stainless steels have conventionally been employed.
However, the sensor ring composed of the sintered body of the ferrite stainless powders may cause cracks in company with corrosion.
The sensor ring is served to engage with an shaft of an opposite matter. When the shaft of the opposite matter is expanded in diameter by corrosion, the elongation of the sensor ring could not follow this expansion and it is the possibility to cause cracks.
For solving such problems, there is a method of heightening the density of the sensor ring by sintering liquid phases. However, this has not been reduced to practice because sizes are considerably varied in the sensor ring requiring high precision.
In the above description, we have explained about the sensor ring. However, these problems also become problems to practically use mechanism parts, particularly, parts used in conditions that it is fitted to or engaged with an opposite part.